Cooling tower with direct and indirect cooling sections

ABSTRACT

A mechanical draft cooling tower includes an air inlet and an air outlet. A liquid spray assembly is provided below the air outlet. A fill shell assembly is provided below the liquid spray assembly such that liquid can be sprayed onto the fill sheet assembly. An indirect heat exchange assembly is mounted beneath the fill sheet assembly. The indirect assembly usually comprises a series of coils through which a fluid to be cooled is circulated. A first air inlet is provided beneath the fill sheet assembly and includes a closing assembly. A second air inlet is provided beneath a top surface of the indirect assembly and includes a closing assembly.

BACKGROUND OF INVENTION

The present invention relates generally to cooling towers, and morespecifically, to an evaporative heat and mass exchanger with a coilmodule for evaporative closed circuit cooling or evaporative condensing.

In an induced draft cross flow or counter flow cooling tower, a fan ismounted in the roof outlet of the tower. This fan draws or inducesairflow inwardly into the cooling tower through a side wall or oppositeside walls of the tower. Water or other evaporative liquid to be cooledis pumped to the top of the cooling tower structure and distributedthrough a series of spray nozzles. These spray nozzles emit a diffusespray of water across the top of a fill media. Such fill media typicallycomprises a bundle of spaced parallel plastic sheets across each ofwhich the water spray is dispersed and downwardly passed by gravity. Thelarge surface area across which the water is dispersed on such sheetsleads to cooling by the induced air flow directed between the sheets.The cold water is collected in a sump and then passed through to thedesired cooling system, wherein it will become heated and then pumpedback to the cooling tower.

An indirect heat exchange unit is provided beneath the bundle of fillsheets. Such unit is typically comprised of serpentine heat exchangeconduits or coils. The hot fluid to be cooled enters the heat exchangeconduits through an inlet header at the lower or bottom edge of theconduits with the cool fluid exiting the conduits through a headerjoining the upper ends of the conduits. Alternately, a vapor to becondensed enters the top of the conduits and as it travels downwardlythrough the conduits becomes condensed and liquefied and exits thebottom header. One such cooling tower apparatus is shown in U.S. Pat.No. 4,683,101. The cooling is provided by sensible cooling from thespray water on the outside of the conduits. Cooling air may or may notflow through the indirect heat exchange unit.

On occasion, such as during cold weather months, it is desired tooperate such cooling towers in a dry mode without the use of water orother fluids being sprayed downwardly across the fill direct heatexchange section. In such an arrangement, it would be desirable to openthe sides of a cooling tower adjacent the indirect cooling section toinflow air. Such an arrangement would optimize the performance of theair-cooled, non evaporative heat exchanger.

Coil shed cooling towers are also known, which consist of a coolingtower with the direct evaporative heat exchanger with fill sectionlocated directly above a non-ventilated indirect cooling or coilsection. Little to no cooling air is drawn through the indirect section.Such coil sheds have little to no cooling capacity when operated withoutthe spray water flowing downwardly over the direct cooling or fillsection. Such limitation on the operation of the tower limits theapplication and utility for such towers as they typically cannot beoperated dry as during the winter months in cold climates. Further, themaximum wet mode performance of the coil or indirect section is limitedas no air enters this section of the cooling tower. The design of thecoil shed cooling tower is such that this section is closed to airinlet. In such an arrangement, it would be desirable to open the sidesof a cooling tower adjacent the indirect cooling section to inflow air.Such an arrangement would optimize the performance of the air-cooled,non evaporative heat exchanger. Referring now to FIG. 3, which shows asection of the cooling tower of FIG. 1, a sliding cover 125 or removablepanel is provided which can be moved to cover air inlet 149 or the fillinlet section 139. Cover 125 can be moved manually or by motor control.

SUMMARY OF THE INVENTION

In one embodiment, the present invention provides a mechanical draftcooling tower comprising an air inlet and an air outlet. A liquid sprayassembly adapted to spray liquid downwardly between the air inlet andthe air outlet is provided. A fill sheet assembly is mounted beneath theliquid spray assembly to provide direct cooling of the liquid sprayflowing downwardly onto the fill sheet assembly.

An indirect heat exchange assembly is mounted beneath the fill sheetassembly. The indirect heat exchange assembly usually comprises a seriesof coils, a collection of plates or other closed type indirect heattransferring assembly. The indirect heat exchange assembly is adapted toreceive a fluid to be cooled and to outlet the fluid after cooling.Alternately, the indirect heat exchange assembly can receive a vapor tobe condensed.

A first air inlet in a side of the cooling tower is provided beneath thefill sheet assembly. A first closing assembly is provided with the firstair inlet whereby the first air inlet can be closed to inlet air. Suchclosing assembly usually comprises a louver or removable cover. A secondair inlet in a side of the cooling tower is provided beneath a topsurface of the indirect heat exchange assembly. A second closingassembly is provided with the second air inlet whereby the second airinlet can be closed to inlet air. The second air inlet typicallycomprises a louver assembly or a removable panel.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is a side view in partial cross section of a cooling tower inaccordance with a first embodiment of the present invention,

FIG. 2 is a side view in partial cross section of a cooling tower inaccordance with a second embodiment of the present invention, and

FIG. 3 is a side view in partial cross section of a cooling tower inaccordance with a third embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to FIG. 1 of the drawings, a cooling tower is showngenerally at 118 and comprises an outlet fan enclosure 112 housing a fan114 therein. Cooling tower 118 is of a generally rectangular or squareshape, comprising an upper surface 116, and end walls 120 and 122. Fan114 induces a draft upwardly and out of outlet fan enclosure 112, withair being drawn inwardly from cooling tower louver fill section opening139 and indirect inlet section 149.

Cooling water is collected in collection sump 124 and is pumped upwardlyvia pump 126 and piping 128. Such cooling water then enters distributionpipe 130, spraying downwardly out of spray nozzles 132 onto fill sectionor direct cooling section 136. Fill section 136 comprises a plurality ofplastic sheets that are stacked or hung within the direct coolingsection of cooling tower 118. Typically such sheets are comprised ofplastic material such as polyvinyl chloride or polypropylene, having agenerally wavy or grooved pattern on both sides to aid in the spreadingrundown and cooling of water exiting from spray nozzles 132.

A baffle arrangement 159 extends inwardly from end walls 120 and 122, aswell as side walls of the cooling tower to assure that the water exitingfill section 136 is distributed evenly and completely across the exposedarea of indirect cooling section coil 142. Such coil 142 usuallycomprises the plurality of coil sections, each of which extends from,when the unit is operating as a fluid cooler, a coil inlet header 152,and exiting at a coil outlet header 150. When the unit is operating as acondenser, the fluid would enter header 150 as a vapor that requirescondensing. The condensed liquid would exit through header 152. Ineither case, the cooling is accomplished by the water flow downwardlyfrom fill section 136 across the coil section 142.

Fill section inlet 139 can be comprised of a louver arrangement, such asshown in FIG. 1, or removable covers or caps that can close off inletair from entering the section of the cooling tower beneath fill section136. This is an option given to the operator of the cooling tower tochoose whether or not air is to be allowed to enter through fill sectionof louvers or opening 139.

Further, air inlet 149 includes a louver or a similar panel or cover,which can close air inlet opening 149 to inlet air. This again gives theoperator of the cooling tower an option whether or not such inlet air isdesired. In such an arrangement, it would be desirable to open the sidesof a cooling tower adjacent the indirect cooling section to inflow air.Such an arrangement would optimize the performance of the air-cooled,non evaporative heat exchanger. Referring now to FIG. 3, which shows asection of the cooling tower of FIG. 1, a sliding cover 125 is providedwhich can be moved to cover air inlet 149 or the fill inlet section 139.Cover 125 can be moved manually or by motor control.

It can be seen that in the embodiment shown in FIG. 1, virtually all ofair inlet 139 is located beneath fill section 136. This can be anoptional arrangement with the portion of air inlet 139 in otherembodiments being allowed to extend upwardly toward and into lateralspacing even with the portion of fill section 136.

Similarly, air inlet 149 is seen to be laterally aligned such that amajority of the air inlet 149 is located beneath the top of indirectcoil cooling section 142.

Referring now to FIG. 2 of the drawings, a cooling tower is showngenerally at 10 comprising an outlet fan enclosure 12, which houses afan 14 therein. Upper surface 16 is seen to comprise a structural roofof cooling tower 10, with side walls 110 and end wall 20 and 22,comprising a generally rectangular shape of cooling tower 10. Basesection 18 is seen to be a structural support for the cooling tower,with sump 24 collecting the water from the cooling tower and pump 26being utilized to pump the water to be cooled upwardly through piping 28to distribution pipe 30. Distribution pipe 30 is seen to extend intodistribution containers 34, with spray nozzles 32 extending from thebottom of distribution container 34.

In the cross-flow cooling tower arrangement shown in FIG. 2, twoseparate distribution containers 34 are shown, with one being at endwall or air inlet 20 and the other being at end wall or air inlet 22. Aseach section of the cooling tower is identical, only one will bedescribed. Fill bundle 36 is seen to comprise a plurality of plasticsheets hung from beams 111 supported at ends with brackets attached toend walls 110. Each of the sheets of fill bundle 36 is comprised ofplastic material such as polyvinyl chloride or polypropylene, having agenerally wavy and grooved pattern on both sides to aid in thespreading, rundown and cooling of water exiting from spray nozzles 32.Drift eliminator 38 assures the cooling water in fill section 36 doesnot enter air inlet chamber 40, which is centrally located in coolingtower 10. Generally, drift eliminator 38 comprises a series of closelyspaced plastic louvers.

A coil heat exchanger assembly 42 is located beneath each fill bundle36. Fluid to be cooled enters cooling tower 10 through conduit 58 andflows upwardly through manifold 54 and through manifold inlets 52 intoeach coil assembly module 60 of coil heat exchanger 64. Cold liquid,having passed through coil heat exchangers 42, exits each coil assemblymodule 60 through outlet 50 into outlet manifold 48 and exits coolingtower 10 through outlet conduit 44. In an alternative embodiment, asingle coil assembly module 60 would be utilized. Alternately, when theunit is operating as a condenser, the fluid enters conduit 44 as a vaporthat requires condensing. The condensed liquid would exit throughconduit 58.

The air inlet side 37 of end wall 20 is seen to include louvers 49. Suchlouvers may be replaced with a panel or other removable piece. However,the function of louvers 49 or the replaceable panel is the same in thatair inlet through air inlet 37 may be either permitted or closed,depending on intended operation of cooling tower 10. It is seen that themajority of air inlet 37 and louvers 49 are laterally spaced beneath thetop of coil assembly 42.

Similarly, air inlet louvers 39 are placed in end wall 20 adjacent fillsection 36. Such louvers can be replaced with a panel or other removablepiece, but the function is the same, depending on the intended operationof cooling tower 10. Such louvers may be closed or panel piece insertedto close air inlet through the inlet section adjacent fill section 36.

1. A mechanical draft cooling tower comprising: an air inlet and an airoutlet, a liquid spray assembly adapted to spray liquid downwardlybetween the air inlet and the air outlet, a fill sheet assembly mountedbeneath the liquid spray assembly, an indirect heat exchange assemblymounted beneath the fill sheet assembly, the indirect heat exchangeassembly adapted to receive a fluid to be cooled and to outlet the fluidafter cooling, a first air inlet in a side of the cooling tower, a firstclosing assembly whereby the first air inlet can be closed to inlet air,a second air inlet in a side of the cooling tower, a majority of thesecond air inlet being located beneath a top surface of the indirectheat exchange assembly, a second closing assembly whereby the second airinlet can be closed to inlet air.
 2. The cooling tower of claim 1wherein the first closing assembly comprises a panel that can beinstalled or removed from the cooling tower side.
 3. The cooling towerof claim 1 wherein the second closing assembly comprises louvers thatcan be opened and closed.
 4. The cooling tower of claim 1 wherein thesecond closing assembly comprises a panel that can be installed orremoved from the cooling tower side.
 5. The cooling tower of claim 1wherein the fill sheet assembly is removable for operation of thecooling tower without operation of the liquid spray assembly.
 6. Thecooling tower of claim 1 wherein the fill sheet assembly comprises twoseparate fill sections, one fill section adjacent one side of thecooling tower and the other fill section adjacent an opposite side ofthe cooling tower.
 7. The cooling tower of claim 1 wherein the indirectheat exchange assembly comprises two separate heat exchange sections,one heat exchange section adjacent one side of the cooling tower and theother fill section adjacent an opposite side of the cooling tower. 8.The cooling tower of claim 1 wherein the fill sheet assembly comprisestwo separate fill sections, one fill section adjacent one side of thecooling tower and the other fill section adjacent an opposite side ofthe cooling tower, wherein the indirect heat exchange assembly comprisestwo separate heat exchange sections, one heat exchange section adjacentone side of the cooling tower and the other fill section adjacent anopposite side of the cooling tower, and wherein the air outlet islocated above and between the two separate fill sections.
 9. The coolingtower of claim 8 wherein air flow is drawn across the fill section andupwardly out the air outlet.
 10. The cooling tower of claim 8 whereinair flow is drawn across the indirect exchange sections and upwardly outthe air outlet.